This invention relates generally to an image formation apparatus which uses a plurality of light emitting elements and, more particularly, to such a system in which an array of such light emitting elements are matched with a lens array for enhancing the illumination pattern preferentially in one direction.
An array of surface-emitting light-emitting diodes (LEDs) is typically manufactured with a 2-dimensional array of the different structures, such as in a Red-Green-Blue (RGB) array where each individual color LED pixel is in the shape of a stripe having an active area whose length is several times greater than its width. The normal optical properties of these LEDs are that the emitted radiation would be in an isotropic pattern, close to a Lambertian.
The isotropic distribution of illumination, which does not favor any one direction or orientation over another, may be the ideal arrangement for some display uses. One example where isotropic illumination may be desired is with a scoreboard at a professional sporting event where fans within the stadium are at all positions relative to the scoreboard—higher, lower, to the left, right and straight on, etc.
Where viewing is predicable, such as billboard signs along a highway, isotropic light distribution is wasteful since only persons in front of and slightly below the sign will be reading the information on the sign. Lenticular arrays, such as fresnel lenses, have been used to focus light from a general light source in a particular direction. But until now, no lens system has specifically addressed LED or pixel-based systems. The present system is adapted to address this deficiency.